Nonlinear magnetic fields in conjunction with tune modulation can lead to chaotic particle motion and thereby limit the dynamic aperture of hadron storage rings. This is of particular interest for the LHC at injection energy where the field errors of the superconducting magnets and the beam size have their maximum.The SPS dynamic aperture experiment was performed to study a controlled nonlinear machine under the influence of tune modulation. In parallel long-term tracking simulations were done to test to which extend computer programs can predict the dynamic aperture under those conditions. In a complementary experiment at the HERA proton ring the dynamic aperture was measured at injection energy under normal operating conditions. The computer simulations for these measurements included a very detailed model of the nonlinear magnetic fields which were measured for each individual magnet.
Various processes will lead to emittance growth in RHIC during injection. The effects of steering errors, optical mismatch, space charge and intrabeam scattering are estimated. The transverse and longitudinal emittance growths are computed for protons and fully stripped gold ions.
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